<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		 <style>
        * {
            padding: 0;
            margin: 0;
            text-align: center;
        }

        .wrap {
            width: 500px;
            margin: 100px auto 0;
        }

        table {
            border-collapse: collapse;
            border-spacing: 0;
            border: 1px solid #c0c0c0;
            width: 500px;
        }

        th,
        td {
            border: 1px solid #d0d0d0;
            color: #404060;
            padding: 10px;
        }

        th {
            background-color: #09c;
            font: bold 16px "微软雅黑";
            color: #fff;
        }

        td {
            font: 14px "微软雅黑";
        }

        tbody tr {
            background-color: #f0f0f0;
            cursor: pointer;
        }
        
        .current {
            background-color: red!important;
        }
    </style>
	</head>
	<body>
		<div class="wrap">
        <table>
            <thead>
                <tr>
                    <th>序号</th>
                    <th>姓名</th>
                    <th>课程</th>
                    <th>成绩</th>
                </tr>
            </thead>
            <tbody id="target">
                <tr>
                    <td>
                        1
                    </td>
                    <td>吕不韦</td>
                    <td>语文</td>
                    <td>100</td>

                </tr>
                <tr>
                    <td>
                        2
                    </td>
                    <td>吕布</td>
                    <td>日语</td>
                    <td>100</td>
                </tr>
                <tr>
                    <td>
                        3
                    </td>
                    <td>吕蒙</td>
                    <td>营销学</td>
                    <td>100</td>
                </tr>
                <tr>
                    <td>
                        4
                    </td>
                    <td>吕尚</td>
                    <td>数学</td>
                    <td>100</td>
                </tr>
                <tr>
                    <td>
                        5
                    </td>
                    <td>吕雉</td>
                    <td>英语</td>
                    <td>100</td>
                </tr>
                <tr>
                    <td>
                        6
                    </td>
                    <td>吕超</td>
                    <td>体育</td>
                    <td>100</td>
                </tr>
            </tbody>
        </table>
    </div>

	</body>
	<script>
		 //需求：让tr各行变色，鼠标放入tr中，高亮显示。
		 //1.隔行变色。
	    var tbody = document.getElementById("target");
	    var trArr = tbody.children;
	    //循环判断并各行赋值属性（背景色）
	    for (var i = 0; i < trArr.length; i++) {
	        if (i % 2 !== 0) {
	            trArr[i].style.backgroundColor = "#a3a3a3";
	        } else {
	            trArr[i].style.backgroundColor = "#ccc";
	        }
	
	        //鼠标进入高亮显示
	
	        var myColor = "";
	        trArr[i].onmouseover = function () {
	            //赋值颜色之前，先记录颜色
	            myColor = this.style.backgroundColor;
	            this.style.backgroundColor = "#fff";
	        }
	        trArr[i].onmouseout = function () {
	            this.style.backgroundColor = myColor;
	        }
	    }
	</script>
</html>